使用RelativeSource和AncestorType进行WPF数据绑定

Question

I am trying to get some binding code working. Bascially I want to bind the IsEnabled property of an element of my grid's context menu with a value of the selected row in the grid.

I have it working with this:

            <my:DataGrid.ContextMenu>
                <ContextMenu DataContext="{Binding PlacementTarget.SelectedItem, RelativeSource={RelativeSource Self}}"> 
                    <MenuItem Header="Grant Access" IsEnabled="{Binding Connectable}"/>
                </ContextMenu>
            </my:DataGrid.ContextMenu>

But I want to do it this way and it's not working. It doesn't error but just doesn't disable the menu item. Any idea why?

            <my:DataGrid.ContextMenu>
                <ContextMenu> 
                    <MenuItem Header="Grant Access" IsEnabled="{Binding Path=SelectedItem.Connectable, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type my:DataGrid}}}"/>
                </ContextMenu>
            </my:DataGrid.ContextMenu>

Answer 1

Try using ElementName binding instead of Ancestor binding . ContextMenu is not part of Grid's visual tree.

--edit--

Ah, I was wrong. ElementName binding (example given below) would also not work with ContextMenu. It is not part of DataGrid's visual tree. That is why it cannot see that DataGrid and thus cannot reference it. You will have to do it using the first method.

Any reason why you don't want to do it that way?

            <DataGrid.ContextMenu>
                <ContextMenu DataContext="{Binding SelectedItem, ElementName=DataGrid1}">
                    <MenuItem Header="Grant Access"
                              IsEnabled="{Binding Connectable}" />
                </ContextMenu>
            </DataGrid.ContextMenu>

Answer 2

如果在调试模式下查看Visual Studio中的输出窗口，您将获得绑定错误的详细信息 - 这可能会对您的问题有所了解。